1. Field of the Invention
The present invention is in the fields of solid-state physics and semiconductor materials, and more particularly concerns bandgap energy engineering analysis for new semiconductor alloy systems comprising hybrid epitaxial semiconductor crystal structures on heterogeneous substrates, including combinations of cubic, trigonal and hexagonal crystal materials.
2. Description of the Related Art
For the last 60 years since the invention of the first transistor by Bardeen, Brattain, and Shockley in 1947, the global microelectronics industry has used diamond structured group IV semiconductor crystals such as silicon (Si) and germanium (Ge). Another cubic compound semiconductor crystal structure, i.e. zinc-blende-alpha structure with group III-V and group II-VI, was also utilized by the semiconductor industry for the last 30 years. In the early 1990s, new semiconductor materials in different crystal structures were introduced in the microelectronics industry, including gallium nitride (GaN), aluminum nitride (AlN), and indium nitride (InN) in wurtzite structure. (See S. Nakamura, T. Mukai T, M. Senoh, Japanese Journal Of Applied Physics Part 2-Letters 30 (12a): L1998-L2001 Dec. 1, 1991.)
The term “bandgap” generally refers to the energy difference between the top of the valence hand and the bottom of the conduction band of a material, the energy gap that enables electrons to jump from one band to another. “Bandgap engineering” is the process of controlling or altering the bandgap of a material by controlling the composition of its constituent semiconductor alloys. Bandgap energy is a fundamental design parameter for semiconductor compositions, and has been particularly important in the design of heterojunction devices, as well as photoelectric devices such as laser diodes and solar cells.
The last 60 years of combined global effort in the field has resulted in a compilation of data showing bandgap energy as a function of the lattice constants associated with various semiconductor alloy compositions, for the diamond, zinc-blende and wurtzite structured materials referred to above. (See, e.g., V. Swaminathan, A. T. Macrander, Materials Aspects of GaAs and InP Based Structures, published by Prentice-Hall, p. 25 (1991); O. Ambacher, Journal of Physics D-Applied Physics 31 (20): 2653-2710 Oct. 21, 1998.)
The present work, including the other disclosures listed above which have been incorporated by reference herein, has involved development of new semiconductor materials with rhombohedral super-hetero epitaxial structures in various combinations of cubic, trigonal and hexagonal crystalline structures. The methods of determining lattice constants that underlie conventional bandgap engineering approaches translate directly to these new materials. Therefore, there was a need to develop a generalized engineering framework for relating these various crystal combinations, particularly in “super-hetero-epitaxial” combinations (i.e., epitaxial growth of one material on a different material with different crystal structure, and for specifying the bandgap energy engineering applicable to these classes of compositions.